<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>isLowerCase</title>
</head>

<body>
    <script>
        const isLowerCase = str => str === str.toLowerCase();
        document.write(`isLowerCase('abc')的结果是:${isLowerCase('abc')}`)
    </script>
</body>

</html>